Why does a low-oxygen environment promote healing?

That's a very good question. Many people believe that wound healing requires a lot of oxygen, so a low-oxygen environment should theoretically slow down healing. However, clinical observations have shown that moderate hypoxia can actually promote wound healing at certain stages. This is due to precise regulation at the cellular biological level, which is quite different from intuition. 

Hypoxia activates key signals for healing

Once a wound forms, local blood vessels rupture, interrupting blood supply. The central area of the wound is naturally hypoxic, with oxygen partial pressure possibly only 10% to 20% of that in normal tissue. The body treats this hypoxia as a trigger signal. Under hypoxic conditions, hypoxia-inducible factors within cells stabilize and enter the cell nucleus, initiating the expression of a series of genes. These genes encode proteins including vascular endothelial growth factor (VEGF), which stimulates new blood vessel ingrowth into the wound; platelet-derived growth factor (PDGF), which recruits fibroblasts and macrophages to the wound site; and glycolysis-related enzymes, enabling cells to produce energy even under hypoxic conditions. Simply put, the hypoxic environment tells cells that there is a problem and repair is needed. Upon receiving this signal, cells begin to proliferate, migrate, and synthesize collagen. Without this hypoxic signal, cells may not even be aware of the wound, and the repair process would be slow to begin.

Hypoxia promotes cell migration and proliferation 

In in vitro cell culture experiments, it was observed that keratinocytes migrated significantly faster under hypoxic conditions than under normoxic conditions. Keratinocytes are the main cells responsible for covering the wound surface; they need to migrate from the wound edge towards the center until the entire wound is covered. Under hypoxia, cytoskeleton remodeling is more active, and pseudopodia extend from the cell tip more quickly. Simultaneously, hypoxia inhibits keratinocyte differentiation, keeping them in a proliferative state rather than prematurely maturing into epidermal cells. This is beneficial for wound healing, as a sufficient number of cells are needed to cover the wound before they gradually differentiate and mature. In contrast, normoxic environments cause keratinocytes to initiate differentiation prematurely; the cells flatten and harden before their numbers have increased sufficiently, and their migration rate actually decreases. 

Phased coordination of hypoxia and normoxic conditions

Hypoxia promotes healing primarily during the early and middle stages of wound healing, namely the inflammatory and proliferative phases. This phase requires rapid initiation of the repair process, significant cell proliferation, and the establishment of new blood vessels. Once the wound base is filled with granulation tissue and the new blood vessel network is largely formed, the oxygen partial pressure at the wound site naturally returns to normal levels. This marks the beginning of the remodeling phase, which requires the reorganization of the extracellular matrix and the arrangement of collagen fibers. This process actually demands even more oxygen. Therefore, in clinical practice, creating a hypoxic microenvironment with occlusive dressings in the early stages after skin grafting helps with graft survival and vascular recanalization. However, once the graft has fully survived, it is no longer necessary to deliberately maintain hypoxia. This is why the use of functional dressings is phased; different dressings are selected for different healing stages, rather than using the same dressing for the entire healing process.

It's important to note that low oxygen levels are not the same as hypoxia.

It's important to distinguish between two concepts here: hypoxia and hypoxia. Hypoxia refers to a state where the oxygen partial pressure is below normal physiological levels but still sufficient to meet the basic metabolic needs of cells, typically around 10% to 20% oxygen concentration. Hypoxia, on the other hand, refers to a state where the oxygen partial pressure is so low that cells cannot maintain normal function and may even begin to die, such as below 1% to 5%. Clinically, the claim that hypoxia promotes healing refers to the former. If a wound is completely sealed with an airtight material, oxygen cannot enter and carbon dioxide cannot escape, causing the wound to transition from hypoxia to hypoxia, leading to cell death. This would not promote healing but rather worsen the damage. This is why qualified medical occlusive dressings are designed with appropriate water vapor permeability and a certain oxygen permeability, allowing the wound to remain within the ideal hypoxic range, rather than completely blocking gas exchange. Therefore, the claim that hypoxia promotes healing is valid only if there is a limit; too much of a good thing can be bad. For more information on Innomed® Silicone Foam Dressing, refer to the Previous Articles. If you have customized needs, you are welcome to contact us; You Wholeheartedly. At long-term medical, we transform this data by innovating and developing products that make life easier for those who need loving care.

Editor: kiki Jia